I am booting into a new KDE install and I just get a black screen and a "Add Widgets" bar across the bottom.
Right-click give a 3 item menu: Desktop & Wallpaper, Display Config, and Enter Edit Mode.
Display config causes a system crash due to Qt6 I think
Adding DESKTOP_SESSION=plasma and QT_STYLE_OVERRIDE=breeze to /etc/environment seemed to help.
I was able to add the Application Launcher to the widget bar.
Related: https://wiki.artixlinux.org/Main/Troubleshooting#Plasma.2FWayland_immediately_crashes_back_to_SDDM
To recap, I have a working KDE with apps, that I can use in either X11 or Wayland, but I had to set up the panel from scratch.